What determines immediate postoperative coronal balance and delayed global coronal balance after anterior spinal fusion for Lenke 5C curves?

Abstract

To determine the factors associated with 6-week postoperative global coronal balance and delayed global coronal balance at 2-year follow-up after anterior spinal fusion for Lenke 5C curves. A total of 124 consecutive Lenke 5C curves with minimum 2-year follow-up was studied. Radiographic parameters were studied preoperatively, 6 weeks postoperatively, and 2years postoperatively. Coronal balance was measured by C7-CSVL and trunk shift < 20mm. The study outcomes were patients with early coronal balance and those who had immediate imbalance but developed delayed balance. Multivariate regression analyses of associated factors were performed with cutoffs determined by receiver operating characteristic curve. 31.5% patients attained global coronal balance immediate postoperatively and 89.4% of the early imbalance cases showed spontaneous coronal balance at 2-year follow-up. Increased preoperative UIV tilt (OR 1.093; p = 0.026; 95% CI: 1.011-1.182) and reduced immediate postoperative RSH difference (OR 0.963; p = 0.015; 95% CI: 0.935-0.993) were associated with immediate postoperative balance. For those with immediate imbalance, larger preoperative major Cobb angle (OR 1.226; p = 0.047; 95% CI: 1.003-1.499), less preoperative C7-CSVL (OR 0.829; p = 0.016; 95% CI: 0.712-0.966), and less immediate postoperative LIV tilt (OR 0.728; p = 0.013; 95% CI: 0.567-0.934) were associated with 2-year coronal balance. There was significant improvement in function (p = 0.006), self-image (p = 0.039) and total score domains (p = 0.014) in immediate imbalance to 2-year balance and imbalance groups. Successful balance is achieved with a parallel fusion mass when performing anterior spinal fusion for Lenke 5C curves. Patients should be reassured that most attain eventual coronal balance despite the early imbalance. Level of evidence Therapeutic III.